Optical properties of germanium quantum dots

We report a combined theoretical and experimental investigation of quantum confinement effects on the E-1 interband structures in the optical spectra of Ge quantum dots. The experimental average radius goes from approximate to 12 to approximate to 60 Angstrom. A blueshift of the E-1 absorption peak (up to 0.1 eV) and a strong reduction in the oscillator strength, are measured effects of the quantum confinement. The theoretical analysis is performed for nanocrystals up to 15 Angstrom through a semi-empirical tight-binding approach. We overcome the single-particle scheme including, in a perturbative approach. the Coulomb electron-hole interaction which induces a red-shift of the E-1 peak with respect to the one-electron calculation.